1. Field of the Invention
The present invention relates generally to the field of optical components. In particular, the present invention relates to methods of forming optical components, for example, waveguides, filters, optical interconnects, lenses, diffraction gratings, and other elements, using multi-photon absorption.
2. Description of the Related Art
Signal transmission using pulse sequences of light is becoming increasingly important in high-speed communications over length scales of from 0.01 to 1 meter. For example, optical integrated circuits (OICs) are gaining importance for high bandwidth optical interconnects on printed wiring boards. As a result, the integration of optical components such as waveguides, filters, optical interconnects, lenses, diffraction gratings, and the like, onto printed wiring boards (PWBs) is becoming increasingly important.
Optical waveguides are typically constructed by surrounding a core material with a clad layer. Optical radiation propagates in the core material because the clad layer has a lower index of refraction than the core material. This condition satisfies the requirements for total internal reflection within the core. Waveguides may be used individually or as an array supported on a substrate. The waveguides often perform a passive function on the optical radiation. For example, splitters divide an optical signal in one waveguide into two or more waveguides; couplers add an optical signal from two or more waveguides into a smaller number of waveguides; and wavelength division multiplexing (“WDM”) structures separate an input optical signal into spectrally discrete output signals, each of which couples to separate waveguides, usually by employing either phase array designs or gratings. Spectral filters, polarizers, and isolators may be incorporated into the waveguide design. As well, waveguides may alternatively contain active functionality, wherein the input signal is altered by interaction with a second optical or electrical signal. Exemplary active functionality includes amplification and switching such as with electro-optic, thermo-optic or acousto-optic devices.
Known methods of manufacturing optical waveguides include, for example, manually placing glass fibers into hollowed out areas on a substrate; filling a mold of a desired structure with a polymeric material that is thermally cured and later removed from the mold; and depositing an optical material on a substrate and patterning using reactive ion etching (RIE) processes. Each of these processes has drawbacks, however, such as requiring multiple steps to define the waveguide, potential sidewall roughness issues, limited resolution, incompatibility with PWB manufacturing schemes and high labor costs.
The use of photoimageable materials in forming optical components such as planar waveguides has also been proposed. In the case of planar waveguides, for example, a photoimageable core layer is deposited over a first clad layer. The core layer is then patterned using standard uv exposure and standard development techniques, and a second clad layer is deposited over the first clad layer and the patterned core structure. This process allows for further reduction in the number of processing steps over the aforementioned techniques.
International publication number WO 01/96917 A2 discloses the use of multiphoton-induced photopolymerization methods for fabricating optically functional elements. Imagewise multiphoton polymerization and blanket irradiation techniques are combined to fabricate optical elements in situ in an encapsulating, protective monolithic polymeric matrix. Various examples of suitable photopolymerizable groups are disclosed, with acryl and (meth)acryl, free radically polymerizable moieties being specified as most preferred.
There are, however, various drawbacks associated with the use of acrylates in forming optical components. For example, acrylates are generally not suitable for use in high temperature applications, for example, in chip-to-chip applications. At temperatures approaching 200° C., most acrylate materials begin to decompose and depolymerize, giving rise to reliability problems in the form, for example, of degradation in optical performance. Moreover, acrylates suffer from the disadvantage of being structurally and optically dissimilar to glass. Glass, being the current material of choice for optical fibers' and pigtail structures, provides beneficial structural and optical properties. In order to reduce problems associated with optical loss, it is desirable to employ materials for optical components having properties more closely matching those of glass than do acrylates.
There is thus a need in the optoelectronics industry for improved methods of forming optical components, as well as for optical components and electronic devices formed therefrom.